Liquid crystal display device

ABSTRACT

A liquid crystal display device includes first and second substrates, a plurality of gate bus lines and data bus lines on the first substrate, the gate bus lines being perpendicular to the data bus lines, a plurality of pixels defined by the gate bus lines and the data bus lines, the pixels having a plularity of regions, at least a pair of electrodes in each region having a common direction, and a plurality of liquid crystal molecules between the substrates.

This application claims the benefit of Korean application No. 1996-23115filed on Jun. 22, 1996, which is hereby incorporated by reference.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to an in-plane switching mode liquid crystal displaydevice (LCD). Although the present invention is suitable for a widescope of applications, it is particularly suitable for improving thequality of picture image.

2. Discussion of the Related Art

As a thin film transistor liquid crystal display device (TFT-LCD) hasbeen widely used for portable televisions or notebook computers, an LCDhaving a large panel is in great demand. A conventional TFT-LCD,however, has a problem that a contrast ratio is changed with a directionof viewing-angle. Liquid crystal display devices such as a twistednematic LCD having an optical compensator and a multi-domain LCD havebeen proposed to cope with this problem. Nevertheless, such LCDs are notcapable of solving the problem in a variation of the contrast ratio andcolor shifting.

An in-plane switching mode LCD to realize a wide viewing angle has alsobeen proposed in the JAPAN DISPLAY 92 Page 457, Japanese PatentUnexamined Publication No. 7-36058, Japanese Patent UnexaminedPublication No. 7-225538, and ASIA DISPLAY 95 Page 707.

A conventional in-plane switching mode LCD will now be explained withreference to FIGS. 1 to 3.

Referring first to FIGS. 1 and 2, operation of the conventional LCD willbe described as follows. Liquid crystal molecules 8 in a liquid crystallayer 12 are aligned to have a rubbing direction (θ_(R)) of90°<θ_(R)<180° with respect to a longitudinal elongation direction(0°)of a gate bus line on a substrate as shown in FIG. 2. A polarizationaxis direction (θ_(PL2)) of a analyzer 10 attached on a second substrate5 is parallel to the rubbing direction (θ_(R)) . A polarization axisdirection(θ_(PL1)) of a polarizer 9 attached on the first substrate 1 isperpendicular to a polarization axis direction (θ_(PL2)) and electrodeelongation directions (θ_(EL)) of a data electrode 2 and a commonelectrode 3 are θ_(EL)=90° with respect to the longitudinal elongationdirection of the gate bus line. Thus, when a voltage is not applied to adata electrode 2 and a common electrode 3 as shown in FIG. 1A, theliquid crystal molecules 8 are aligned with a slightly tilted directionrelative to the elongation direction(θ_(EL)) of the data and commonelectrodes along with the rubbing direction(θ_(R)) in the substrate. Theelongation direction(θ_(EL)) of the electrodes is perpendicular to thelongitudinal direction of the gate bus line. Conversely, when a voltagehaving a horizontal electric field parallel to the longitudinaldirection of the gate bus line is applied to the liquid crystal layer 12as shown in FIG. 1E, the liquid crystal molecules 8 near the firstsubstrate are rotated and a transmittance of the liquid crystal layer 12is changed by a birefringence. A retardation value (Δnd) of the liquidcrystal layer 12 is about λ/2 (for example, And would be approximately0.21-0.36 μm, where λ is a wavelength of an incident light). Forexample, when the liquid crystal rotation angle is about 45 degree, thetransmittance is maximum so that a screen of the LCD becomes a blackmode.

FIG.3A is a plane view of the conventional in-plane switching modeliquid crystal display device and FIG. 3B is a cross-sectional viewtaken along the line A-A′ in FIG.3A. The liquid crystal display deviceis protected by a metal frame 22 excluding a representing unit 21 of aliquid crystal panel 32. A gate driving circuit 23, a data drivingcircuit 24, and a back light housing 25 including a back light 31 aremounted on the metal frame 22. In the representing unit 21, an exposureplate 75 (shown in FIG. 3B) having a light diffusion plate, polarizer63, first and second substrates 27 and 26 constituting the liquidcrystal panel 32, and an analyzer 64 are disposed on the secondsubstrate 26. Further, a light compensator (not shown) may be disposedbetween the polarizer 63 and the first substrate 27 or between thesecond substrate 26 and the analyzer 64 to improve the contrast ratio.

Generally, in the conventional TFT-LCD, the TFT is formed in the firstsubstrate 27 as a switching device and the color filter is formed on thesecond substrate 26. However, a diode may be used as a switching devicein a diode LCD and a simple matrix LCD. Alternatively, when the TFT isformed on the second substrate, the color filter is formed onto thefirst substrate. Further, a mono-chromiumatic LCD may also be usedwithout the color filter.

However, the conventional in-plane switching mode liquid crystal displaydevice has a problem of the color shifting with the change of viewingangle direction. As shown in FIGS. 1C to 1D, when a horizontal electricfield is applied to the electrodes 2, 3, the liquid crystal molecules 8nearby the first substrate 1 are aligned parallel to the longitudinaldirection of the gate bus line, whereas the liquid crystal molecules 8nearby the second substrate 5 are aligned with an angle of 90°-180°relative to the longitudinal direction of the gate bus line. The liquidcrystal molecules 8 are thus twisted. Therefore, color shifting iscaused in either blue or yellow in a X or Y viewing angle direction,respectively. This color shifting mainly deteriorates the quality of thepicture image.

SUMMARY OF INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide an in-plane switchingmode liquid crystal display device having an improved picture imagequality by preventing color shifting.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a liquidcrystal display device includes a substrate, a gate bus line and a databus line elongating horizontally and vertically to form a matrix figure,a pixel which is divided into several regions defined by the gate busline and the data bus line, a data electrode and a common electrode ineach region of the pixel, and alignment layer over the substrate.

In another aspect of the present invention, a liquid crystal displaydevice includes first and second substrates, a plurality of gate buslines and data bus lines on the first substrate, the gate bus linesbeing perpendicular to the data bus lines, a plurality of pixels definedby the gate bus lines and the data bus lines, the pixels having aplurality of regions, at least a pair of electrodes in each regionhaving a common direction, and a plurality of liquid crystal moleculesbetween the substrates.

In another aspect of the present invention, a liquid crystal displaydevice includes first and second substrates, a plurality of gate buslines and data bus lines on the first substrate in a matrix form, aplurality of pixels defined by the gate bus lines and the data buslines, the pixels having first and second regions, at least one commonbus line at each pixel, the common bus line being parallel to the gatebus line, at least a pair of first and second electrodes in the firstand second regions, respectively, the first and second electrodes havingfirst and second electrode elongation directions (θ_(EL1) and θ_(EL2))with respect to a longitudinal direction of the common bus line, a colorfilter layer over the second substrate, first and second alignmentlayers over the first and second substrates, the first and secondalignment layers having first and second alignment directions (θ_(R1)and θ_(R2)), respectively, a liquid crystal layer between the firstsubstrate and the second substrate, a polarizer and a analyzer attachedto the first substrate and the second substrate, respectively.

In another aspect of the present invention, A liquid crystal displaydevice having a plurality of pixels each including a plurality ofregions, the device includes first and second substrates, a liquidcrystal molecular layer having liquid crystal molecules between thefirst and second substrates, a plurality of electrodes in each region ofthe pixels, an electric field parallel to the substrates applying to theelectrodes, and first and second alignment layers over the first andsecond substrates, respectively, the first and second alignment layershaving first and second alignment directions of θ1 and θ2 relative to anelectrode elongating direction.

In a further aspect of the present invention, a liquid crystal displaydevice having a plurality of pixels each including a plurality ofregions, the device includes first and second substrates, a liquidcrystal molecular layer having liquid crystal molecules between thefirst and second substrates, a plurality of electrodes on the firstsubstrate in each region of the pixels, an electric field parallel tothe substrates applying to the electrodes, a different electric fieldfrom that of a neighboring region to rotate the liquid crystal moleculesin opposite directions in each neighboring region applying to theelectrodes in each region, and first and second alignment layers overthe first and second substrates, the first and second alignment layersproviding for first and second alignment directions of θ₁ and θ₂.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIGS. 1A to 1D are schematic views illustrating an operation of aconventional in-plane switching mode liquid crystal display device.

FIG. 2 illustrates an axis directional relationship in the conventionalin-plane switching mode liquid crystal display device.

FIG. 3A illustrates the conventional in-plane switching mode liquidcrystal display device.

FIG. 3B is a cross-sectional view of the conventional in plane switchingmode liquid crystal display device taken along the line A-A′ in FIG. 3A.

FIG. 4 is a plane view of a liquid crystal display device in accordancewith a first embodiment of the present invention.

FIG. 5 is a cross-sectional view taken along the line B-B′ of FIG.4.

FIG. 6 illustrates an axis directional relationship of the in-planeswitching mode liquid crystal display device in accordance with thefirst embodiment of the present invention.

FIGS. 7A to 7D are schematic views illustrating an operation of thein-plane switching mode liquid crystal display device in accordance withthe first embodiment of the present invention.

FIG. 8A illustrates a gray invention region in the conventional in-planeswitching mode liquid crystal display device.

FIG. 8B illustrates a gray inversion region of the in-plane switchingmode liquid crystal display device in accordance with the firstembodiment of the present invention.

FIG. 9 illustrates a driving voltage waveform of the in-plane switchingmode liquid crystal display device in accordance with the firstembodiment of the present invention.

FIG. 10 is a plane view of the in-plane switching mode liquid crystaldisplay device in accordance with a second embodiment of the presentinvention.

FIG. 11 is an axis directional relationship of the in-plane switchingmode liquid crystal display device in accordance with the secondembodiment of the present invention.

FIG. 12 is a plane view of the in-plane switching mode liquid crystaldisplay device in accordance with a third embodiment of the presentinvention.

FIG. 13 is an axis directional relationship of the in-plane switchingmode liquid crystal display device in accordance with the thirdembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

Hereinafter, an in-plane switching mode liquid crystal display deviceaccording to a first embodiment of the present invention will bedescribed with reference to FIGS. 4 to 9.

Referring to FIGS. 4 and 5, a liquid crystal panel includes a TFT 55, acolor filter layer 61, alignment layers 59, 62 over the first and secondsubstrates 27, 26, respectively, a liquid crystal layer 60, and a spacer65 between the first and second substrates 27, 26 to maintain a constantdistance between the substrates 27, 26 and a polarizer on both surfacesof the liquid crystal panel.

In FIG. 4, the TFT 55 on the first substrate 27 is disposed at a regionwhere a gate bus line 41 and data bus line 42 are crossedperpendicularly with each other. A common bus line 43 parallel to thegate bus line 41 is formed in the center of a pixel in a matrix form. Acommon electrode 49 connected to the common bus line 43 is formed in thepixel. A data electrode 48 connected to the drain electrode 47 of theTFT 55 is formed in parallel to the common electrode 49.

Referring to FIGS. 5 and 6, the pixel is divided into a first region Iand a second region II the by common bus line 43. θ_(EL1) is anelectrode elongation direction in the first region I, and θ_(PL1) is apolarization direction of polarizer 63. θ_(EL2) is an electrodeelongation direction in the second region II, and θ_(PL2) is apolarization direction of analyzer 64. θ_(R) is a rubbing direction,θ_(LC1) and θ_(LC2) are optical axis directions of a liquid crystalmolecules in the first and second region, respectively. Electrodeelongation directions of the first region I and the second region II aresymmetric to the common bus line 43. Thus, the angles θ_(EL1), θ_(EL2)of the electrodes in each region I, II relative to the common bus line43 are the same. A voltage is applied to the gate bus line 41 in thelongitudinal direction of the liquid crystal display device. The rubbingdirection of the first substrate 27 is not parallel to that of thesecond substrate 26. The rubbing direction is parallel to thepolarization direction(θ_(PL2)) of the analyzer 64. The polarizationdirection(θ_(PL2)) of the analyzer 64 is perpendicular to thepolarization direction(θ_(PL1)) of the polarizer 63.

The gate bus line 41, the common bus line 43, and the common electrode49 are made of an AlTa thin film (3% Ta content) having a thickness of0.3 μm deposited by a sputtering process. The AlTa thin film surface isanodized to form the AlTa oxidation layer 52 having a thickness of 0.1μm, so that the electrode surface has a higher insulationcharacteristic. Also, a short circuit due to a thin thickness isprevented on the electrode surface. After a gate insulating layer 57having a thickness of 0.3 μm, an amorphous silicon (a-si) layer 44having a thickness of 0.2 μm, and n⁺-Si layer are consecutivelydeposited on the AlTa oxidation layer 52 by PECVD (plasma enhancedchemical vapor deposition), a photoetching process is executed to formthe TFT 55.

Then, a chromium layer having a thickness of 0.1 μm is deposited on theTFT 55 and etched by the sputtering process. A photoetching process isfurther conducted to form a source electrode 46, drain electrode 47 ofthe TFT 55, and the data electrode 48. The n⁺-silicon layer on a channelunit of the TFT 55 is removed by a dry-etching process using the sourceelectrode 46 and the drain electrode 47 as masks. Thus, a-Si layerremains only on the channel unit. Thereafter, a passivation layer 58having a thickness of 0.2 μm is deposited on the entire surface over thefirst substrate 27 by PECVD. For example, Si_(x)N_(y) may be used as thepassivation layer 58. Subsequently, the passivation layer 58 ispartially etched on the end portion of the gate bus line 41 and data busline 42 to connect the bus lines 41, 42 with the outer driver circuit.

A storage capacitor 53 (shown in FIG. 4) is formed at an overlappingregion of the common bus line 43 and a data electrode 48. The storagecapacitor 53 maintains uniform the electric charges of the data voltagein the each pixel.

A black matrix 51 (shown in FIG. 5) and a color filter layer 61 areformed on the second substrate 26. An overcoat layer (not shown) isformed on the black matrix 51 and the color filter layer 61 to obtainthe high stability of the surface and improve the flatness. The blackmatrix 51 prevents the leakage of light at the gate bus line 41, thedata bus line 42, the common bus line 43, and the TFT 55. The blackmatrix 51 is formed by, etching a Cr/Cr_(x)O_(y) layer having athickness of about 0.1 μm in each region. R, G, and B layers are formedrespectively on the color filter layer of the each pixel.

In the aforementioned-structure of the LCD, the widths of data electrode48, the common electrode 49 and the gap between the electrodes are 5 μmeach.

An alignment layers 59, 62 are formed on the first and second substrates27 and 20 by depositing and baking a serial No.RN1024 of Nissan Chemicalhaving a thickness of 0.08 μm. While the alignment layer 59 over thefirst substrate 27 is rubbed in the direction of −90° with respect toelongation direction of the common bus line, the alignment layer 62 onthe second substrate is rubbed in the direction of 90°. For a spacer 65,a Micropearl of SEKISUI FINE-CHEMICAL having a diameter of 6.4 μm isused to have a liquid crystal layer 60 having a thickness of 6.2 μm. Andfor liquid crystals, a positive liquid crystal such as ZGS5025(Δn=0.067, Δε=6.0) of CHISSO CO. is used. At this time, the pre-tiltangle of the aligned liquid crystal molecules is about 4.8°, and theretardation value (Δnd) is about=0.41.

The optical transmission axis direction (θ_(PL1)) of the polarizer 63attached to the first substrate 27 is parallel to the longitudinaldirection of the gate bus line 41. The optical transmission axisdirection (θ_(PL2)) of the analyzer 64 attached to the second substrate26 is perpendicular to the longitudinal direction of the gate bus line41.

The gap between the data electrode 48 and the common electrode 49 isthinner than a thickness of liquid crystal layer and the retardationvalue (Δnd) of the liquid crystal satisfies the following equation.λ/2<Δnd≦λwhere, Δn is an anisotropy of a refractive index of the liquid crystal,d is a thickness of the liquid crystal layer, and λis a wavelength.

The data electrode 48 and the common electrode 49 in the first region Iand the second region II are formed to have angles θ_(EL1) and θ_(EL2),respectively, with respect to the common bus line 43. The data electrode48 and the common electrode 49 are symmetric with each other.

Operation of the present in-plane switching mode liquid crystal displaydevice will now be described with reference to FIGS. 7A to 7D. FIGS. 7Aand 7B are cross-sectional views of the in-plane switching mode liquidcrystal display device and a plane view of off-state LCD, and FIGS. 7Cand 7D are for on-state LCD, respectively.

The elongated direction of the conventional electrodes has an angle of90° relative to the longitudinal direction(0°) of the gate bus line.However, the electrodes of the present invention on the first region Iand the second region II are respectively extended in the directionswith angles θ_(EL1) and θ_(EL2) relative to the longitudinal directionof the gate electrode. The electrodes in the first region I and in thesecond region II are thus symmetric with each other. Here, the value ofthe angles satisfies the following equations.0°<θ_(EL1)<90°, −90°<θ_(EL2)<0 °, and |θ_(EL1)|=|θ_(EL2)|.

When the voltage is not applied to the electrodes, the optical axis ofall the liquid crystal molecules in the liquid crystal layer, set inbetween the first substrate 27 and the second substrate 26 is alignedalmost parallel to the substrate by the alignment layer 59, 62, as shownFIGS. 7A and 7B. For example, the liquid crystals between the substratesare nematic liquid crystals without a choral dopant. A light 11 incidentto the first substrate 27 is polarized linearly by the polarizer 63,transmitted to the liquid crystal layer 60, and reaches the analyzer 64.However, since the polarization directions of the analyzer 64 and thepolarizer 63 are perpendicular with each other, the light 11 is nottransmitted to the analyzer 64. Therefore, the LCD screen becomes ablack mode.

Conversely, when the voltage is applied to the electrodes 48, 49, aparallel electric field 13 is applied in the liquid crystal layer 60through a data voltage between the data electrode 48 and the commonelectrode 49. The parallel electric field 13 has a maximum value (E₁) onthe surface of an alignment layer 59 of first substrate 27, a nearthreshold value (E₂) on the surface of the alignment layer 62 of thesecond substrate 26, and a medium value (E_(M)=(E₁+E₂) /2) in the middleof the liquid crystal layer. When the parallel electric field 13 is notuniform, the intensity of the parallel electric field 13 becomesgradually smaller from the first substrate 27 to the second substrate26. Such a non-uniform electric field in the liquid crystal layer 60 canbe formed by making the thickness of the liquid crystal layer. 60 largerthan the gap between the electrodes. A liquid crystal molecule 77 a,which is near the surface of alignment layer 59 in the first region I,is affected by the non-uniform electric field. The optical axisdirection (θ_(LC1)) of the liquid crystal molecules is thus changed tobe perpendicular to the electrode elongation direction (θ_(EL1)).

Similarly, in a liquid crystal molecule 77 b near the surface ofalignment layer 59 in the second region II, the optical axis direction(θ_(LC2)) is also changed to be perpendicular to the electrodeelongation direction (θ_(EL2)) in the second region II. Further, sincethe electric field applied to the liquid crystal molecules 78 a, 78 bnear the surface of the alignment layer 62 in the regions I, II is thenear threshold value, the molecules 78 a, 78 b are not affected by theelectric field so that the optical axis is not changed. Therefore, byapplying the non-uniform electric field, the liquid crystal molecules inthe liquid crystal layer between the substrates 26, 27 are graduallychanged from the first substrate 27 to the second substrate 26. As aresult, the molecules are in a twisted state.

The liquid crystal molecules 77 a, 78 a are twisted counterclockwisefrom a direction parallel to the rubbing direction (θ_(R)). Thedirection is perpendicular to the longitudinal direction of the gate busline 41 and the direction of θ_(LC1) in the first region I. The liquidcrystal molecules 77 b, 78 b are twisted clockwise from a directionperpendicular to the longitudinal direction of the gate bus line 41 andthe θ_(LC2) in the second region II. As a result, the liquid crystalmolecules in the first region I and the second region II are twisted inthe opposite direction with each other.

When the linearly polarized light 11 through the polarizer 63 istransmitted to the liquid crystal layer 60, the polarization directionof the light is rotated by the twisted liquid crystal layer 60 and theoptical axis direction is directed to the same direction of thepolarization direction in the analyzer 64. The light 11 linearlypolarized by the polarizer 63 and transmitted to the liquid crystallayer 60 is thus transmitted to the analyzer so that the LCD screenbecomes a white mode.

Here, the amount of the light transmittance depends on the twisted angleof the liquid crystal molecules. Thus, when the twisted angle of theliquid crystal molecules become larger, the amount of lighttransmittance also becomes larger. A grey level of the liquid crystaldisplay device can also be controlled with the data voltage by twistingthe liquid crystal molecules.

For example, when the voltage applied to the electrode is 1V-5V, theliquid crystal molecules in the first region I and the second region IIare arranged symmetrically with each other by the electric field of theeach region having an intermediate grey level. Thus, the color shiftingoccurred in the viewing angle directions of X, Y the first region I andthe second region II is different from each other. The viewing angledirection of X causes the blue shift and the viewing angle direction ofY causes the yellow shift in the first region I. On the other hand, theviewing angle direction of X causes the yellow shift and the viewingangle direction of Y causes the blue shift in the second region II.Therefore, the total color shifting caused by the birefringence ratio ofthe liquid crystal molecules is corrected by the color shifting in thefirst and second regions I, II, so that the desired color can beobtained in whole pixels.

In order to maximize the optical transmittance ratio of the liquidcrystal layer 60 at the maximum voltage, the retardation value (Δnd) ofthe liquid crystal layer 60 must be about 0.74λ. Accordingly, theanisotropy of the refractive index (Δn) and a thickness of the liquidcrystal layer (d) has to be limited to get the maximum opticaltransmittance ratio. The general twist nematic liquid crystal layer hasthe anisotropy of refractive index of about 0.06-0.09 and the thicknessof 6.0-8.8 μm when the wavelength of the incident light is about 0.56μm.

FIG.8A and FIG. 8B illustrate the viewing angle characteristicsaccording to the conventional in-plane switching liquid crystal displaydevice and the first embodiment in-plane switching liquid crystaldisplay device, respectively. Hatched regions are viewing angle regionswith the contrast ratio of 10:1 or less. As shown in FIG.8A, the regionshave the lower contrast ratio at four inclined viewing angle directionin the conventional liquid crystal display device.

In the present liquid crystal display device, the regions also have thelower contrast ratio at four inclined viewing angle direction, as shownin FIG. 8B, but the regions are much smaller than the regions in theconventional LCD. That is, the liquid crystal display device of thepresent invention provides regions having a contrast ratio more than10:1 is larger than the conventional in-plane switching LCD. Also, theviewing angle characteristic is improved in both the vertical andhorizontal directions. This results from the color shifting according tothe viewing angle becomes smaller and the contrast ratio of the screenis increased.

FIG. 9 is a driving voltage waveform of the liquid crystal displaydevice according to the first embodiment. For example, in thisembodiment, the screen size is 12.1 inch and the pixel number of 480*640(*R·G·B). A gate voltage V_(GH), ground voltage V_(GL), and commonvoltage V_(CO) are 20, 0, and 8V, respectively, and a pulse width is 31μs. The data voltage V_(D) is taken as a single pulse signal having afrequency of 31 μs, and a maximum ±6V, and minimum ±1V with respect tothe common voltage V_(CO). The data voltage V_(D) may be controlled tohave 5V in the signal region. Also, by adjusting the common voltage, theAC voltage is applied between the common electrode 49 and the dataelectrode 48.

Materials for the alignment layers on the first substrate and the secondsubstrate do not have to be the same in the present invention. On thefirst substrate, for example, the alignment layer including a materialhaving a lower anchoring energy and a lower rubbing density may becoated to rotate the liquid crystal molecules easily. On the other hand,the alignment layer such as polygamic acids base material having a lowerpre-tilt angle and good absorption characteristics of impurity from theliquid crystal may be coated on the second substrate to improve theviewing angle characteristics and remove the after-image.

Also, the pixel is divided into the first region and the second regionin the first embodiment. Moreover, when the pixel is divided into morethan two regions, the first region and the second region may be arrangedto have more effective liquid crystal display devices.

Referring to FIGS. 10 and 11, a second embodiment in the presentinvention will be described as following. As shown in the FIG. 10, thepixel is divided into a first region I and second region II. A commonbus line 153 is formed between the regions I and II. A common electrode148 in the second region II is connected to a source electrode 147 ofthe TFT. The common electrode 148 in the first region is elongated inthe directions of θ_(EL1)=90° relative to longitudinal direction of thegate bus line 141 (i.e., 0° in FIG. 11) and 90°<θ_(EL2)<180° in thesecond region. A rubbing angle direction (θ_(R)) in the alignment layeris relative to the longitudinal direction of the gate bus line 141. Theangle θ_(R) of the rubbing direction in the alignment layer is largerthan the angle θ_(EL1) of the electrode elongation direction in thefirst region, and smaller than the angle θ_(EL2) of the electrodeelongation direction in the second region. Thus, the relationship amongthe angles of θ_(EL1) , θ_(R), θ_(EL2), is, θ_(EL1)<θ_(R)<θ_(EL2).

Therefore, the liquid crystal molecules in the first region I and thesecond region II are aligned symmetrically with each other and rotatedin the opposite direction with each other having the intermediate greylevel in the applied voltage state. Therefore, the color shiftingaccording to the viewing angle direction is compensated as similarly inthe first embodiment.

Referring to FIGS. 12 and 13 a third embodiment will be described. Anoptical axis direction of the pixel is shown in FIG. 13. While theelectrode elongation direction is divided into several regions in thepixel in the first and second embodiments, the electrode elongationdirection of all of the pixel is the same and a rubbing direction isdifferent from each region. Further, it is possible to control thealignment state of the liquid crystal molecules in each region in thethird embodiment. The angles θ_(EL1), θ_(EL2) of electrode elongationdirections on the first region I and the second region II areθ_(EL1)=90°, θ_(EL2)=90°, respectively, relative to the longitudinaldirection (shown as 0° in FIG. 13) of the gate bus line 241, and theangles θ_(R1), θ_(R2) of rubbing directions in each region are0°<θ_(R1)<90°,−90°<θ_(R2)<0°. Also, the relationship between the rubbingdirection (θ_(R1)) of the first region I and the rubbing direction(θ_(R2)) of the second region II is θ_(R1)=−θ_(R2). The liquid crystalmolecules on the first region I and the second region II are thusrotated clockwise and counterclockwise, respectively. The molecules arein the opposite direction with each other at an intermediate grey levelin the applied voltage state and aligned symmetrically relative to thelongitudinal direction of the gate bus line 241. Thus, the colorshifting according to viewing angle direction is compensated in thisembodiment.

The rubbing process is to determine the alignment direction of thealignment layer in the each embodiments. The alignment direction mayalso be determined by irradiating the ultraviolet light into thealignment layer using the light alignment material as an alignmentlayer.

The present invention provides an in-plan switching mode liquid crystaldisplay device that the pixel is divided into a plurality of regions.The data electrode and the common electrode of each region are symmetricrelative to the longitudinal direction of the gate bus line. Theelectrode elongation direction is in common relative to the longitudinaldirection of the gate bus line and the rubbing directions are differentfrom each region. The color shifting is, thus corrected by thebirefringence of the liquid crystals.

Further, since the rotation angle of the twisted liquid crystalmolecules is large, the liquid crystal layer may be formed with a largethickness. The inexpensive driving IC may be used to maintain themaximum transmittance ratio because of the lower driving voltage. Also,the light through the liquid crystal layer remains in the linearlypolarized state without using the polarizer so that the production costis reduced for color shift correction. Moreover, a liquid crystaldisplay device having a high reliability may be fabricated with theconventional twisted nematic liquid crystal in the present invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice of the present invention without departing from the spirit orscope of the invention. Thus, it is intended that the present inventioncover the modifications and variations of this invention provided theycome within the scope of the appended claims and their equivalents.

1. A liquid crystal display device, comprising: first and secondsubstrates; a plurality of gate bus lines and data bus lines on thefirst substrate, the gate bus lines being perpendicular to the data buslines; a plurality of pixels defined by the gate bus lines and the databus lines, the pixels having a plularity of regions; at least a pair ofelectrodes in each region having a common direction; and a plurality ofliquid crystal molecules between the substrates.
 2. The device accordingto claim 1, wherein the electrodes include a data electrode and a commonelectrode.
 3. The device according to claim 1, wherein an electric fieldhaving an intensity changing gradually from the first substrate to thesecond substrate is applied to the liquid crystal molecules.
 4. Thedevice according to claim 3, wherein the liquid crystal molecules arerotated gradually from the first substrate to the second substrate whenthe electric field is applied to the electrodes.
 5. A liquid crystaldisplay device,.comprising: first and second substrates; a plurality ofgate bus lines and data bus lines on the first substrate in a matrixform; a plurality of pixels defined by the gate bus lines and the databus lines, the pixels having first and second regions; at least onecommon bus line at each pixel, the common bus line being parallel to thegate bus line; at least a pair of first and second electrodes in thefirst and second regions, respectively, the first and second electrodeshaving first and second electrode elongation directions (θ_(EL1) andθ_(EL2)) with respect to a longitudinal direction of the common busline; a color filter layer over the second substrate; first and secondalignment layers over the first and second substrates, the first andsecond alignment layers having first and second alignment directions(θ_(R1) and θ_(R2)) respectively; a liquid crystal layer between thefirst substrate and the second substrate; a polarizer and a analyzerattached to the first substrate and the second substrate, respectively.6. The device according to claim 5, wherein the electrodes are separatedby a distance smaller than a thickness of the liquid crystal layer. 7.The device according to claim 5, wherein the liquid crystal layer has aretardation value(Δnd) of λ/2<Δnd<λ (where Δn is an anisotropy of arefractive index, d is a thickness of the liquid crystal layer, and λ isa wavelength of an incident light).
 8. The device according to claim 7,wherein the retardation value is approximately 0.74λ.
 9. The deviceaccording to claim 5, wherein the first alignment layer has an anchoringenergy lower than that of the second alignment layer.
 10. The deviceaccording to claim 9, wherein the second alignment layer includes apolygamic acid base material.
 11. The device according to claim 5,wherein the first and second alignment layers have rubbing directionsparallel to a polarized direction of the analyzer.
 12. The deviceaccordance to claim 11, wherein the polarizer has a polarized directionperpendicular to the polarized direction of the analyzer.
 13. The deviceaccording to claim 5, wherein the first electrode elongation directionhas an absolute value the same as that of the second electrodeelongation direction.
 14. The device according to claim 5, wherein thefirst and second electrode elongation directions are between 0° and 90°and between −90° and 0°, respectively.
 15. The device according to claim14, wherein the first and second electrode elongation directions are−90° and 90° with respect to a longitudinal direction of the gate buslines, respectively.
 16. The device according to claim 5, wherein thefirst and second electrode elongation directions are 90° and between 90°and 180°, respectively.
 17. The device according to claim 16, whereinthe θ_(EL1)<θ_(R1)<θ_(EL2) and the θ_(R2)=180°−θ_(EL1).
 18. The deviceaccording to claim 5, wherein the first and second electrode elongationdirections have complementary angles with respect to the longitudinaldirection of the common bus line.
 19. The device according to claim 18,wherein the first and second alignment directions have ranges of0°<θ_(R1)<90° and −90°<θ_(2R)<0° with respect to the common bus line,respectively.
 20. The device in accordance with claim 19, wherein thefirst and second alignment directions have a relationship ofθ_(R1)=−θ_(R2).
 21. The device according to claim 5, further comprisinga first optical compensator between the polarizer and the firstsubstrate.
 22. The device according to claim 5, further comprising asecond optical compensator between the second substrate and theanalyzer.
 23. A liquid crystal display device having a plurality ofpixels each including a plurality of regions, the device comprising:first and second substrates; a liquid crystal molecular layer havingliquid crystal molecules between the first and second substrates; aplurality of electrodes in each region of the pixels, an electric fieldparallel to the substrates being applied to the electrodes; and firstand second alignment layers over the first and second substrates,respectively, the first and second alignment layers having firsthandsecond alignment,directions of θ1 and θ2. relative to an electrodeelongating direction.
 24. The device according to claim 23, wherein theliquid crystal molecules in each region and a neighboring region arerotated in directions opposite with each other when an electric field isapplied in the device.
 25. The device according to claim 23, wherein theelectrodes include at least a pair of electrodes.
 26. The deviceaccording to claim 25, wherein the pair of electrodes include a dataelectrode and a common electrode.
 27. The device according to claim 25,wherein a gap between the pair of electrodes is smaller than a thicknessof the liquid crystal molecular layer.
 28. The device according to claim23, wherein the first alignment direction is 0°<θ₁<90°.
 29. The deviceaccording to claim 23, wherein the second alignment direction is−90°<θ₂<0°.
 30. The device according to claim 23, wherein the first andsecond alignment directions have a relationship of θ₁=−θ₂.
 31. Thedevice according to claim 23, wherein the liquid crystal layer has aretardation value Δnd of λ/2 (Δnd≦λ(where Δn is an anisotropy of arefractive index, d is thickness of the liquid crystal molecular layer,and λ is a wavelength of an incident light).
 32. The device according toclaim 31, wherein the retardation value is about 0.74λ.
 33. A liquidcrystal display device having a plurality of pixels each including aplurality of regions, the device comprising: first and secondsubstrates; a liquid crystal molecular layer having liquid crystalmolecules between the first and second substrates; a plurality ofelectrodes on the first substrate in each region of the pixels, anelectric field parallel to the substrates being applied to theelectrodes, which is different from the electric field of a neighboringregion to rotate the liquid crystal molecules in opposite directions ineach neighboring region applying to the electrodes in each region; andfirst and second alignment layers over the first and second substrates,the first and second alignment layers providing for first and secondalignment directions of θ₁ and θ₂ with respect to a longitudinaldirection of a common bus line,.
 34. The device according to claim 33,wherein the electrodes includes at least a pair of electrodes.
 35. Thedevice according to claim 34, wherein the pair of electrodes includes adata electrode and a common electrode.
 36. The device according to claim34, wherein the pair of electrodes have a space therebetween smallerthan a thickness of the liquid crystal molecular layer.
 37. The deviceaccording to claim 33, wherein the first alignment direction has anangle of 0°<θ₁<90°.
 38. The device according to claim 33, wherein thesecond alignment direction has an angle of −90°<θ₂<0°.
 39. The deviceaccording to claim 33, wherein an angle between the first alignmentdirection and the second alignment direction is a supplementary angle.40. The device according to claim 33, wherein the liquid crystalmolecular layer has a retardation value (Δnd) of λ/2<Δnd≦λ (where Δn isan anisotropy of a refractive index, d is a thickness of the liquidcrystal layer, and λ is a wavelength of an incident light).
 41. Thedevice according to claim 39, wherein the retardation value 0.74λ.